The object of the research is to study behavioral implications of beta-alanine and dopamine metabolism in Drosophila under natural and artificial conditions. Laboratory mutant flies, as well as flies extracted directly from nature, which show polymorphism in levels of beta-alanine and dopamine accumulation in the body fluids, are studied. The two species studied are melanogaster and melanica. C-14 labeled substances are used as metabolic tracers. Behavior is studied in an illumination- humidity gradient. Special attention is placed on microhabitat selection and differential mating success. Similar studies are made with flies artificially injected with beta-alanine or dopamine during development to produce behavioral phenocopies. Differential fitness of the color phases if determined by laboratory population studies. Desiccation resistance of the color phases is also tested.